Light sensitive display

ABSTRACT

A light sensitive display.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to touch sensitive displays.

[0002] Touch sensitive screens (“touch screens”) are devices thattypically mount over a display such as a cathode ray tube. With a touchscreen, a user can select from options displayed on the display'sviewing surface by touching the surface adjacent to the desired option,or, in some designs, touching the option directly. Common techniquesemployed in these devices for detecting the location of a touch includemechanical buttons, crossed beams of infrared light, acoustic surfacewaves, capacitance sensing, and resistive materials.

[0003] For example, Kasday, U.S. Pat. No. 4,484,179 discloses anoptically-based touch screen comprising a flexible clear membranesupported above a glass screen whose edges are fitted with photodiodes.When the membrane is flexed into contact with the screen by a touch,light which previously would have passed through the membrane and glassscreen is trapped between the screen surfaces by total internalreflection. This trapped light travels to the edge of the glass screenwhere it is detected by the photodiodes which produce a correspondingoutput signal. The touch position is determined by coordinating theposition of the CRT raster beam with the timing of the output signalsfrom the several photodiodes. The optically-based touch screen increasesthe expense of the display, and increases the complexity of the display.

[0004] Denlinger, U.S. Pat. No. 4,782,328 on the other hand, relies onreflection of ambient light from the actual touch source, such as afinger or pointer, into a pair of photosensors mounted at corners of thetouch screen. By measuring the intensity of the reflected light receivedby each photosensor, a computer calculates the location of the touchsource with reference to the light received by each photosensor, acomputer calculates the location of the touch source with reference tothe screen. The inclusion of the photosensors and associated computerincreases the expense of the display, and increases the complexity ofthe display.

[0005] May, U.S. Pat. No. 5,105,186, discloses a liquid crystal touchscreen that includes an upper glass sheet and a lower glass sheetseparated by spacers. Sandwiched between the glass sheets is a thinlayer of liquid crystal material. The inner surface of each piece ofglass is coated with a transparent, conductive layer of metal oxide.Affixed to the outer surface of the upper glass sheet is an upperpolarizer which comprises the display's viewing surface. Affixed to theouter surface of glass sheet is a lower polarizer. Forming the backsurface of the liquid crystal display is a transflector adjacent to thelower polarizer. A transflector transmits some of the light striking itssurface and reflects some light. Adjacent to transflector is a lightdetecting array of light dependent resistors whose resistance varieswith the intensity of light detected. The resistance increases as thelight intensity decreases, such as occurs when a shadow is cast on theviewing surface. The light detecting array detect a change in the lighttransmitted through the transflector caused by a touching of viewingsurface. Similar to touch sensitive structures affixed to the front ofthe liquid crystal stack, the light sensitive material affixed to therear of the liquid crystal stack similarly pose potential problemslimiting contrast of the display, increasing the expense of the display,and increasing the complexity of the display.

[0006] Touch screens that have a transparent surface which mountsbetween the user and the display's viewing surface have severaldrawbacks. For example, the transparent surface, and other layersbetween the liquid crystal material and the transparent surface mayresult in multiple reflections which decreases the display's contrastand produces glare. Moreover, adding an additional touch panel to thedisplay increases the manufacturing expense of the display and increasesthe complexity of the display. Also, the incorporation of the touchscreen reduces the overall manufacturing yield of the display.

[0007] Accordingly, what is desired is a touch screen that does notsignificantly decrease the contrast ratio, does not significantlyincrease the glare, does not significantly increase the expense of thedisplay, and does not significantly increase the complexity of thedisplay.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a cross sectional view of a traditional active matrixliquid crystal display.

[0009]FIG. 2 is a schematic of the thin film transistor array.

[0010]FIG. 3 is a layout of the thin film transistor array of FIG. 2.

[0011] FIGS. 4A-4H is a set of steps suitable for constructing pixelelectrodes and amorphous silicon thin-film transistors.

[0012]FIG. 5 illustrates pixel electrodes, color filters, and a blackmatrix.

[0013]FIG. 6 illustrates a schematic of the active matrix elements,pixel electrode, photo TFT, readout TFT, and a black matrix.

[0014]FIG. 7 illustrates a pixel electrode, photo TFT, readout TFT, anda black matrix.

[0015]FIG. 8 is a layout of the thin film transistor array of FIGS. 6and 7.

[0016]FIG. 9 is a graph of the capacitive charge on the light sensitiveelements as a result of touching the display at high ambient lightingconditions.

[0017]FIG. 10 is a graph of the capacitive charge on the light sensitiveelements as a result of touching the display at low ambient lightingconditions.

[0018]FIG. 11 is a graph of the photo-currents in an amorphous siliconTFT array.

[0019]FIG. 12 is a graph of the capacitive charge on the light sensitiveelements as a result of touching the display and providing light from alight wand.

[0020]FIG. 13 is an alternative layout of the pixel electrodes.

[0021]FIG. 14 illustrates a timing set for the layout of FIG. 13.

[0022]FIG. 15 illustrates a handheld device together with an opticalwand.

[0023]FIG. 16 illustrates even/odd frame addressing.

[0024]FIG. 17 illustrates a front illuminated display.

[0025]FIG. 18 illustrates total internal reflections.

[0026]FIG. 19 illustrates a small amount of diffraction of thepropagating light.

[0027]FIG. 20 illustrates significant diffraction as a result of aplastic pen.

[0028]FIG. 21 illustrates a shadow of a pointing device and a shadowwith illuminated region of a pointing device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] Referring to FIG. 1, a liquid crystal display (LCD) 50 (indicatedby a bracket) comprises generally, a backlight 52 and a light valve 54(indicated by a bracket). Since liquid crystals do not emit light, mostLCD panels are backlit with fluorescent tubes or arrays oflight-emitting diodes (LEDs) that are built into the sides or back ofthe panel. To disperse the light and obtain a more uniform intensityover the surface of the display, light from the backlight 52 typicallypasses through a diffuser 56 before impinging on the light valve 54.

[0030] The transmittance of light from the backlight 52 to the eye of aviewer 58, observing an image displayed on the front of the panel, iscontrolled by the light valve 54. The light valve 54 normally includes apair of polarizers 60 and 62 separated by a layer of liquid crystals 64contained in a cell gap between glass or plastic plates, and thepolarizers. Light from the backlight 52 impinging on the first polarizer62 comprises electromagnetic waves vibrating in a plurality of planes.Only that portion of the light vibrating in the plane of the opticalaxis of the polarizer passes through the polarizer. In an LCD lightvalve, the optical axes of the first 62 and second 60 polarizer aretypically arranged at an angle so that light passing through the firstpolarizer would normally be blocked from passing through the secondpolarizer in the series. However, the orientation of the translucentcrystals in the layer of liquid crystals 64 can be locally controlled toeither “twist” the vibratory plane of the light into alignment with theoptical axes of the polarizer, permitting light to pass through thelight valve creating a bright picture element or pixel, or out ofalignment with the optical axis of one of the polarizes, attenuating thelight and creating a darker area of the screen or pixel.

[0031] The surfaces of the a first glass substrate 61 and a second glasssubstrate 63 form the walls of the cell gap are buffed to producemicroscopic grooves to physically align the molecules of liquid crystal64 immediately adjacent to the walls. Molecular forces cause adjacentliquid crystal molecules to attempt to align with their neighbors withthe result that the orientation of the molecules in the column ofmolecules spanning the cell gap twist over the length of the column.Likewise, the plane of vibration of light transiting the column ofmolecules will be “twisted” from the optical axis of the first polarizer62 to a plane determined by the orientation of the liquid crystals atthe opposite wall of the cell gap. If the wall of the cell gap is buffedto align adjacent crystals with the optical axis of the secondpolarizer, light from the backlight 52 can pass through the series ofpolarizers 60 and 62 to produce a lighted area of the display whenviewed from the front of the panel (a “normally white” LCD).

[0032] To darken a pixel and create an image, a voltage, typicallycontrolled by a thin film transistor, is applied to an electrode in anarray of transparent electrodes deposited on the walls of the cell gap.The liquid crystal molecules adjacent to the electrode are attracted bythe field produced by the voltage and rotate to align with the field. Asthe molecules of liquid crystal are rotated by the electric field, thecolumn of crystals is “untwisted,” and the optical axes of the crystalsadjacent to the cell wall are rotated progressively out of alignmentwith the optical axis of the corresponding polarizer progressivelyreducing the local transmittance of the light valve 54 and attenuatingthe luminance of the corresponding pixel. In other words, in a normallywhite twisted nematic device there are generally two modes of operation,one without a voltage applied to the molecules and one with a voltageapplied to the molecules. With a voltage applied (e.g., driven mode) tothe molecules the molecules rotate their polarization axis which resultsin inhibiting the passage of light to the viewer. Similarly, without avoltage applied (e.g., non-driven mode) the polarization axis is notrotated so that the passage of light is not inhibited to the viewer.¹

[0033] Conversely, the polarizers and buffing of the light valve can bearranged to produce a “normally black” LCD having pixels that are dark(light is blocked) when the electrodes are not energized and light whenthe electrodes are energized. Color LCD displays are created by varyingthe intensity of transmitted light for each of a plurality of primarycolor (typically, red, green, and blue) sub-pixels that make up adisplayed pixel.

[0034] The aforementioned example was described with respect to atwisted nematic device. However, this description is only an example andother devices may likewise be used, including but not limited to,multi-domain vertical alignment, patterned vertical alignment, in-planeswitching, and super-twisted nematic type LCDs. In addition otherdevices, such as for example, plasma displays, organic displays, activematrix organic light emitting display, electroluminescent displays,liquid crystal on silicon displays, reflective liquid crystal devicesmay likewise be used. For such displays the light emitting portion ofthe display, or portion of the display that permits the display ofselected portions of light may be considered to selectively cause thepixels to provide light.

[0035] For an active matrix LCD (AMLCD) the inner surface of the secondglass substrate 63 is normally coated with a continuous electrode whilethe first glass substrate 61 is patterned into individual pixelelectrodes. The continuous electrode may be constructed using atransparent electrode, such as indium tin oxide. The first glasssubstrate 61 may include thin film transistors (TFTs) which act asindividual switches for each pixel electrode (or group of pixelelectrodes) corresponding to a pixel (or group of pixels). The TFTs areaddressed by a set of multiplexed electrodes running along the gapsbetween the pixel electrodes. Alternatively the pixel electrodes may beon a different layer from the TFTs. A pixel is addressed by applyingvoltage (or current) to a selected line, which switches the TFT on andallows charge from the data line to flow onto the rear pixel electrodes.The combination of voltages between the front electrode and the pixelelectrodes sets up a voltage across the pixels and turns the respectivepixels on. The thin-film transistors are typically constructed fromamorphous silicon, while other types of switching devices may likewisebe used, such as for example, metal-insulator-metal diode andpolysilicon thin-film transistors. The TFT array and pixel electrodesmay alternatively be on the top of the liquid crystal material. Also,the continuous electrode may be patterned or portions selectivelyselected, as desired. Also the light sensitive elements may likewise belocated on the top, or otherwise above, of the liquid crystal material,if desired.²

[0036] Referring to FIG. 2, the active matrix layer may include a set ofdata lines and a set of select lines. Normally one data line is includedfor each column of pixels across the display and one select line isincluded for each row of pixels down the display, thereby creating anarray of conductive lines. To load the data to the respective pixelsindicating which pixels should be illuminated, normally in a row-by-rowmanner, a set of voltages are imposed on the respective data lines 204which imposes a voltage on the sources 202 of latching transistors 200.The selection of a respective select line 210, interconnected to thegates 212 of the respective latching transistors 200, permits thevoltage imposed on the sources 202 to be passed to the drain 214 of thelatching transistors 200. The drains 214 of the latching transistors 200are electrically connected to respective pixel electrodes and arecapacitively coupled to a respective common line 221 through arespective Cst capacitor 218. In addition, a respective capacitanceexists between the pixel electrodes enclosing the liquid crystalmaterial, noted as capacitances Clc 222 (between the pixel electrodesand the common electrode on the color plate). The common line 221provides a voltage reference. In other words, the voltage data(representative of the image to be displayed) is loaded into the datalines for a row of latching transistors 200 and imposing a voltage onthe select line 210 latches that data into the holding capacitors andhence the pixel electrodes.

[0037] Referring to FIG. 3, a schematic layout is shown of the activematrix layer. The pixel electrodes 230 are generally grouped into a“single” effective pixel so that a corresponding set of pixel electrodes230 may be associated with respective color filters (e.g., red, green,blue). The latching transistors 200 interconnect the respective pixelelectrodes 230 with the data lines and the select line. The pixelelectrodes 230 may be interconnected to the common line 221 by thecapacitors Cst 218.

[0038] Referring to FIG. 4, the active matrix layer may be constructedusing an amorphous silicon thin-film transistor fabrication process. Thesteps may include gate metal deposition (FIG. 4A), aphotolithography/etch (FIG. 4B), a gate insulator and amorphous silicondeposition (FIG. 4C), a photolithography/etch (FIG. 4D), a source/drainmetal deposition (FIG. 4E), a photolithography/etch (FIG. 4F), an ITOdeposition (FIG. 4G), and a photolithography/etch (FIG. 4H). Otherprocesses may likewise be used, as desired.

[0039] The present inventors considered different potentialarchitectural touch panel schemes to incorporate additional opticallayers between the polarizer on the front of the liquid crystal displayand the front of the display. These additional layers include, forexample, glass plates, wire grids, transparent electrodes, plasticplates, spacers, and other materials. In addition, the present inventorsconsidered the additional layers with different optical characteristics,such as for example, birefringence, non-birefringence, narrow range ofwavelengths, wide range of wavelengths, etc. After an extensive analysisof different potential configurations of the touch screen portion addedto the display together with materials having different opticalproperties and further being applied to the different types oftechnologies (e.g., mechanical switches, crossed beams of infraredlight, acoustic surface waves, capacitance sensing, and resistivemembranes), the present inventors determined that an optimized touchscreen is merely a tradeoff between different undesirable properties.Accordingly, the design of an optimized touch screen is an ultimatelyunsolvable task. In contrast to designing an improved touch screen, thepresent inventors came to the realization that modification of thestructure of the active matrix liquid crystal device itself couldprovide an improved touch screen capability without all of the attendantdrawbacks to the touch screen configuration located on the front of thedisplay.

[0040] Referring to FIG. 5, with particular attention to the latchingtransistors of the pixel electrodes, a black matrix 240 is overlying thelatching transistors so that significant ambient light does not strikethe transistors. Color filters 242 may be located above the pixelelectrodes. Ambient light striking the latching transistors results indraining the charge imposed on the pixel electrodes through thetransistor. The discharge of the charge imposed on the pixel electrodesresults in a decrease in the operational characteristics of the display,frequently to the extent that the display is rendered effectivelyinoperative. With the realization that amorphous silicon transistors aresensitive to light incident thereon, the present inventors determinedthat such transistors within the active matrix layer may be used as abasis upon which to detect the existence of or non-existence of ambientlight incident thereon (e.g., relative values thereto).

[0041] Referring to FIG. 6, a modified active matrix layer may include aphoto-sensitive structure or elements. The preferred photo-sensitivestructure includes a photo-sensitive thin film transistor (photo TFT)interconnected to a readout thin film transistor (readout TFT). Acapacitor Cst2 may interconnect the common line to the transistors.Referring to FIG. 7, a black matrix may be in an overlying relationshipto the readout TFT. The black matrix is preferably an opaque material orotherwise the structure of the display selectively inhibiting thetransmission of light to selective portions of the active matrix layer.Preferably the black matrix is completely overlying the amorphoussilicon portion of the readout TFT, and at least partially overlying theamorphous silicon portion of the readout TFT. Preferably the blackmatrix is completely non-overlying the amorphous silicon portion of thephoto TFT, and at least partially non-overlying the amorphous siliconportion of the photo TFT. Overlying does not necessarily denote directcontact between the layers, but is intended to denote in the generalsense the stacked structure of materials. In some embodiments, the blackmatrix inhibits ambient light from impacting the amorphous siliconportion of the readout TFT to an extent greater than inhibiting ambientlight from impacting the amorphous silicon portion of the photo TFT.

[0042] As an example, the common line may be set at a negative voltagepotential, such as −10 volts. During the previous readout cycle, avoltage is imposed on the select line which causes the voltage on thereadout line to be coupled to the drain of the photo TFT and the drainof the readout TFT, which results in a voltage potential across Cst2.The voltage coupled to the drain of the photo TFT and the drain of thereadout TFT is approximately ground (e.g., zero volts) with thenon-inverting input of the operational amplifier connected to ground.The voltage imposed on the select line is removed so that the readoutTFT will turn “off”.

[0043] Under normal operational conditions ambient light from the frontof the display passes through the black matrix and strikes the amorphoussilicon of the photo TFT. However, if a person touches the front of thedisplay in a region over the opening in the black matrix or otherwiseinhibits the passage of light through the front of the display in aregion over the opening in the black matrix, then the photo TFTtransistor will be in an “off” state. If the photo TFT is “off” then thevoltage across the capacitor Cst2 will not significantly dischargethrough the photo TFT. Accordingly, the charge imposed across Cst2 willbe substantially unchanged. In essence, the voltage imposed across Cst2will remain substantially unchanged if the ambient light is inhibitedfrom striking the photo TFT.

[0044] To determine the voltage across the capacitor Cst2, a voltage isimposed on the select line which causes the gate of the readout TFT tointerconnect the imposed voltage on Cst2 to the readout line. If thevoltage imposed on the readout line as a result of activating thereadout TFT is substantially unchanged, then the output of theoperational amplifier will be substantially unchanged (e.g., zero). Inthis manner, the system is able to determine whether the light to thedevice has been inhibited, in which case the system will determine thatthe screen has been touched at the corresponding portion of the displaywith the photo TFT.

[0045] During the readout cycle, the voltage imposed on the select linecauses the voltage on the respective drain of the photo TFT and thedrain of the readout TFT to be coupled to the respective readout line,which results in resetting the voltage potential across Cst2. Thevoltage coupled to the drain of the photo TFT and the drain of thereadout TFT is approximately ground (e.g., zero volts) with thenon-inverting input of the operational amplifier connected to ground.The voltage imposed on the select line is removed so that the readoutTFT will turn “off”. In this manner, the act of reading the voltagesimultaneously acts to reset the voltage potential for the next cycle.

[0046] Under normal operational conditions ambient light from the frontof the display passes through the black matrix and strikes the amorphoussilicon of the photo TFT. If a person does not touch the front of thedisplay in a region over the opening in the black matrix or otherwiseinhibits the passage of light through the front of the display in aregion over the opening in the black matrix, then the photo TFTtransistor will be in an “on” state. If the photo TFT is “on” then thevoltage across the capacitor Cst2 will significantly discharge throughthe photo TFT, which is coupled to the common line. In essence thevoltage imposed across Cst2 will decrease toward the common voltage.Accordingly, the charge imposed across Cst2 will be substantiallychanged in the presence of ambient light. Moreover, there is asubstantial difference in the voltage potential across the holdcapacitor when the light is not inhibited versus when the light isinhibited.

[0047] Similarly, to determine the voltage across the capacitor Cst2, avoltage is imposed on the select line which causes the gate of thereadout TFT to interconnect the imposed voltage to the readout line. Ifthe voltage imposed on the readout line as a result of activating thereadout TFT is substantially changed or otherwise results in aninjection of current, then the output of the operational amplifier willbe substantially non-zero. The output voltage of the operationalamplifier is proportional or otherwise associated with the charge on thecapacitor Cst2. In this manner, the system is able to determine whetherthe light to the device has been uninhibited, in which case the systemwill determine that the screen has not been touched at the correspondingportion of the display with the photo TFT.

[0048] Referring to FIG. 8, a layout of the active matrix layer mayinclude the photo TFT, the capacitor Cst2, the readout TFT in a regionbetween the pixel electrodes. Light sensitive elements are preferablyincluded at selected intervals within the active matrix layer. In thismanner, the device may include touch panel sensitivity without the needfor additional touch panel layers attached to the front of the display.In addition, the additional photo TFT, readout TFT, and capacitor may befabricated together with the remainder of the active matrix layer,without the need for specialized processing. Moreover, the complexity ofthe fabrication process is only slightly increased so that the resultingmanufacturing yield will remain substantially unchanged. It is to beunderstood that other light sensitive elements may likewise be used. Inaddition, it is to be understood that other light sensitive electricalarchitectures may likewise be used.

[0049] Referring to FIG. 11, a graph of the photo-currents withinamorphous silicon TFTs is illustrated. Line 300 illustrates a darkambient environment with the gate connected to the source of the photoTFT. It will be noted that the leakage currents are low and relativelystable over a range of voltages. Line 302 illustrates a dark ambientenvironment with a floating gate of the photo TFT. It will be noted thatthe leakage currents are generally low and relatively unstable over arange of voltages (significant slope). Line 304 illustrates a lowambient environment with the gate connected to the source of the photoTFT. It will be noted that the leakage currents are three orders ofmagnitude higher than the corresponding dark ambient conditions andrelatively stable over a range of voltages. Line 306 illustrates a lowambient environment with a floating gate of the photo TFT. It will benoted that the leakage currents are generally three orders of magnitudehigher and relatively unstable over a range of voltages (significantslope). Line 308 illustrates a high ambient environment with the gateconnected to the source of the photo TFT. It will be noted that theleakage currents are 4.5 orders of magnitude higher than thecorresponding dark ambient conditions and relatively stable over a rangeof voltages. Line 310 illustrates a high ambient environment with afloating gate of the photo TFT. It will be noted that the leakagecurrents are generally 4.5 orders of magnitude higher and relativelyunstable over a range of voltages (significant slope). With thesignificant difference between the dark state, the low ambient state,and the high ambient state, together with the substantially flatresponses over a voltage range (source-drain voltage), the system mayreadily process the data in a confident manner, especially with the gateconnected to the source.

[0050] Referring to FIG. 9, under high ambient lighting conditions thephoto TFT will tend to completely discharge the Cst2 capacitor to thecommon voltage, perhaps with an offset voltage because of the photo TFT.In this manner, all of the photo TFTs across the display will tend todischarge to the same voltage level. Those regions with reduced ambientlighting conditions or otherwise where the user blocks ambient lightfrom reaching the display, the Cst2 capacitor will not fully discharge,as illustrated by the downward spike in the graph. The downward spike inthe graph provides location information related to the region of thedisplay that has been touched.

[0051] Referring to FIG. 10, under lower ambient lighting conditions thephoto TFT will tend to partially discharge the Cst2 capacitor to thecommon voltage. In this manner, all of the photo TFTs across the displaywill tend to discharge to some intermediate voltage levels. Thoseregions with further reduced ambient lighting conditions or otherwisewhere the user blocks ambient light from reaching the display, the Cst2capacitor will discharge to a significantly less extent, as illustratedby the downward spike in the graph. The downward spike in the graphprovides location information related to the region of the display thathas been touched. As shown in FIGS. 9 and 10, the region or regionswhere the user inhibits light from reaching the display may bedetermined as localized minimums. In other embodiments, depending on thecircuit topology, the location(s) where the user inhibits light fromreaching the display may be determined as localized maximums orotherwise some measure from the additional components.

[0052] In the circuit topology illustrated, the value of the capacitorCst2 may be selected such that it is suitable for high ambient lightingconditions or low ambient lighting conditions. For low ambient lightingconditions, a smaller capacitance may be selected so that the device ismore sensitive to changes in light. For high ambient lightingconditions, a larger capacitance may be selected so that the device isless sensitive to changes in light. In addition, the dimensions of thephototransistor may be selected to change the photo-leakage current.Also, one set of light sensitive elements (e.g., the photo TFT and thecapacitance) within the display may be optimized for low ambientlighting conditions while another set of light sensitive elements (e.g.,the photo TFT and the capacitance) within the display may be optimizedfor high ambient lighting conditions. Typically, the data from lightsensitive elements for low ambient conditions and the data from lightsensitive elements for high ambient conditions are separately processed,and the suitable set of data is selected. In this manner, the samedisplay device may be used for high and low ambient lighting conditions.In addition, multiple levels of sensitivity may be provided. It is to beunderstood that a single architecture may be provided with a wide rangeof sensitivity from low to high ambient lighting conditions.

[0053] Another structure that may be included is selecting the value ofthe capacitance so that under normal ambient lighting conditions thecharge on the capacitor only partially discharges. With a structurewhere the capacitive charge only partially discharges, the presentinventors determined that an optical pointing device, such as a lightwand or laser pointer, might be used to point at the display to furtherdischarge particular regions of the display. In this manner, the regionof the display that the optical pointing device remains pointed at maybe detected as local maximums (or otherwise). In addition, those regionsof the display where light is inhibited will appear as local minimums(or otherwise). This provides the capability of detecting not only theabsence of light (e.g., touching the panel) but likewise those regionsof the display that have increased light incident thereon. Referring toFIG. 12, a graph illustrates local minimums (upward peaks) from addedlight and local maximums (downward peaks) from a lack of light. Inaddition, one set of light sensitive elements (e.g., the photo TFT andthe capacitance) within the display may be optimized for ambientlighting conditions to detect the absence of light while another set oflight sensitive elements (e.g., the photo TFT and the capacitance)within the display may be optimized for ambient lighting conditions todetect the additional light imposed thereon.

[0054] A switch associated with the display may be provided to selectamong a plurality of different sets of light sensitive elements. Forexample, one of the switches may select between low, medium, and highambient lighting conditions. For example, another switch may selectbetween a touch sensitive operation (absence of light) and an opticalpointing device (addition of light). In addition, the optical pointingdevice may communicate to the display, such as through a wire orwireless connection, to automatically change to the optical sensingmode.

[0055] It is noted that the teachings herein are likewise applicable totransmissive active matrix liquid crystal devices, reflective activematrix liquid crystal devices, transflective active matrix liquidcrystal devices, etc. In addition, the light sensitive elements maylikewise be provided within a passive liquid crystal display. Thesensing devices may be, for example, photo resistors and photo diodes.

[0056] Alternatively, light sensitive elements may be provided betweenthe rear polarizing element and the active matrix layer. In thisarrangement, the light sensitive elements are preferably fabricated onthe polarizer, or otherwise a film attached to the polarizer. Inaddition, the light sensitive elements may be provided on a thin glassplate between the polarizer and the liquid crystal material. Inaddition, the black matrix or otherwise light inhibiting material ispreferably arranged so as to inhibit ambient light from striking thereadout TFT while free from inhibiting light from striking the photoTFT. Moreover, preferably a light blocking material is provided betweenthe photo TFT and/or the readout TFT and the backlight, such as gatemetal, if provided, to inhibit the light from the backlight fromreaching the photo TFT and/or the readout TFT.

[0057] Alternatively, light sensitive elements may be provided betweenthe front polarizing element and the liquid crystal material. In thisarrangement, the light sensitive elements are preferably fabricated onthe polarizer, or otherwise a film attached to the polarizer. Inaddition, the light sensitive elements may be provided on a thin glassplate between the polarizer and the liquid crystal material. The lightsensitive elements may likewise be fabricated within the front electrodelayer by patterning the front electrode layer and including suitablefabrication techniques. In addition, a black matrix or otherwise lightinhibiting material is preferably arranged so as to inhibit ambientlight from striking the readout TFT while free from inhibiting lightfrom striking the photo TFT. Moreover, preferably a light blockingmaterial is provided between the photo TFT and/or the readout TFT andthe backlight, if provided, to inhibit the light from the backlight fromreaching the photo TFT and/or the readout TFT.

[0058] Alternatively, light sensitive elements may be provided betweenthe front of the display and the rear of the display, normallyfabricated on one of the layers therein or fabricated on a separatelayer provided within the stack of layers within the display. In thecase of a liquid crystal device with a backlight the light sensitiveelements are preferably provided between the front of the display andthe backlight material. The position of the light sensitive elements arepreferably between (or at least partially) the pixel electrodes, whenviewed from a plan view of the display. This may be particularly usefulfor reflective displays where the pixel electrodes are opaque. Inaddition for reflective displays, any reflective conductive electrodesshould be arranged so that they do not significantly inhibit light fromreaching the light sensitive elements.³ In this arrangement, the lightsensitive elements are preferably fabricated on one or more of thelayers, or otherwise a plate attached to one or more of the layers. Inaddition, a black matrix or otherwise light inhibiting material ispreferably arranged so as to inhibit ambient light from striking thereadout TFT while free from inhibiting light from striking the photoTFT. Moreover, preferably a light blocking material is provided betweenthe photo TFT and/or the readout TFT and the backlight, if provided, toinhibit the light from the backlight from reaching the photo TFT and/orthe readout TFT.

[0059] In many applications it is desirable to modify the intensity ofthe backlight for different lighting conditions. For example, in darkambient lighting conditions it may be beneficial to have a dimbacklight. In contrast, in bright ambient lighting conditions it may bebeneficial to have a bright backlight. The integrated light sensitiveelements within the display stack may be used as a measure of theambient lighting conditions to control the intensity of the backlightwithout the need for an additional external photo-sensor. One lightsensitive element may be used, or a plurality of light sensitive elementmay be used together with additional processing, such as averaging.

[0060] In one embodiment, the readout line may be included in a periodicmanner within the display sufficient to generally identify the locationof the “touch”. For example the readout line may be periodically addedat each 30^(th) column. Spacing the readout lines at a significantnumber of pixels apart result in a display that nearly maintains itsprevious brightness because most of the pixel electrodes have anunchanged size. However, after considerable testing it was determinedthat such periodic spacing results in a noticeable non-uniform grayscale because of differences in the size of the active region of thepixel electrodes. One potential resolution of the non-uniform gray scaleis to modify the frame data in a manner consistent with thenon-uniformity, such as increasing the gray level of the pixelelectrodes with a reduced size or otherwise reducing the gray levels ofthe non-reduced size pixel electrodes, or a combination thereof. While apotential resolution, this requires additional data processing whichincreases the computational complexity of the system.

[0061] A more desirable resolution of the non-uniform gray scale is tomodify the display to include a readout line at every third pixel, orotherwise in a manner consistent with the pixel electrode pattern of thedisplay (red pixel, green pixel, blue pixel). Alternatively, a readoutline is included at least every 12^(th) pixel (36 pixel electrodes of ared, blue, green arrangement), more preferably at least every 9^(th)pixel (27 pixel electrodes of a red, blue, green arrangement), even morepreferably at least every 6^(th) pixel (18 pixel electrodes of a red,blue, green arrangement or 24 pixel electrodes of a red, blue, bluegreen arrangement), and most preferably at least every 3^(rd) pixel (3pixel electrodes of a red, blue, green arrangement). The readout linesare preferably included for at least a pattern of four times the spacingbetween readout lines (e.g., 12^(th) pixel times 4 equals 48 pixels,9^(th) pixel times 4 equals 36 pixels). More preferably the patten ofreadout lines is included over a majority of the display. The resultingdisplay may include more readout lines than are necessary to accuratelydetermine the location of the “touch”. To reduce the computationalcomplexity of the display, a selection of the readout lines may be freefrom interconnection or otherwise not operationally interconnected withreadout electronics. In addition, to further reduce the computationalcomplexity of the display and to increase the size of the pixelelectrodes, the readout lines not operationally interconnected withreadout electronics may likewise be free from an associated lightsensitive element. In other words, additional non-operational readoutlines may be included within the display to provide a gray scale displaywith increased uniformity. In an alternative embodiment, one or more ofthe non-operational readout lines may be replaced with spaces. In thismanner, the gray scale display may include increased uniformity, albeitwith additional spaces within the pixel electrode matrix.

[0062] The present inventors considered the selection of potential pixelelectrodes and came to the realization that the electrode correspondingto “blue” light does not contribute to the overall white transmission tothe extent that the “green” or “red” electrodes. Accordingly, the systemmay be designed in such a manner that the light sensitive elements areassociated with the “blue” electrodes to an extent greater than theirassociation with the “green” or “red” electrodes. In this manner, the“blue” pixel electrodes may be decreased in size to accommodate thelight sensitive elements while the white transmission remainssubstantially unchanged. Experiments have shown that reducing the sizeof the “blue” electrodes to approximately 85% of their original size,with the “green” and “red” electrodes remaining unchanged, results in areduction in the white transmission by only about 3 percent.⁴

[0063] While such an additional set of non-operational readout linesprovides for increased uniform gray levels, the reduction of pixelapertures results in a reduction of brightness normally by at least 5percent and possibly as much as 15 percent depending on the resolutionand layout design rules employed. In addition, the manufacturing yieldis decreased because the readout line has a tendency to short to itsneighboring data line if the processing characteristics are notaccurately controlled. For example, the data line and readout line maybe approximately 6-10 microns apart along a majority of their length.

[0064] Referring to FIG. 13, to increase the potential manufacturingyield and the brightness of the display, the present inventors came tothe realization that the readout of the photo-sensitive circuit and thewriting of data to the pixels may be combined on the same bus line, orotherwise a set of lines that are electrically interconnected to oneanother. To facilitate the use of the same bus line, a switch 418 mayselect between providing new data 420 to the selected pixels and readingdata 414 from the selected pixels. With the switch 418 set tointerconnect the new data 420 with the selected pixels, the data from aframe buffer or otherwise the video data stream may be provided to thepixels associated with one of the select lines. Multiple readoutcircuits may be used, or one or more multiplexed readout circuits maybeused. For example, the new data 420 provided on data line 400 may be 4.5volts which is latched to the pixel electrode 402 and the photo TFT 404by imposing a suitable voltage on the select line 406. In this manner,the data voltage is latched to both the pixel electrode and acorresponding photo-sensitive circuit.

[0065] The display is illuminated in a traditional manner and thevoltage imposed on the photo TFT 404 may be modified in accordance withthe light incident on the photo-sensitive circuit, as previouslydescribed. In the topology illustrated, the photo TFT 404 is normally aN-type transistor which is reverse biased by setting the voltage on thecommon line 408 to a voltage lower than an anticipated voltage on thephoto TFT 404, such as −10 or −15 volts. The data for the current framemay be stored in a frame buffer for later usage. Prior to writing thedata for another frame, such as the next frame, the data (e.g., voltage)on the readout TFT 410 is read out. The switch 418 changes between thenew data 420 to the readout line 414 interconnected to the chargereadout amplifier 412. The select line 406 is again selected to couplethe remaining voltage on the photo TFT 404 through the readout TFT 410to the data line 400. The coupled voltage (or current) to the data line400 is provided as an input to the charge readout amplifier 412 which iscompared against the corresponding data from the previous frame 422,namely, the voltage originally imposed on the photo TFT 404. Thedifference between the readout line 414 and the data from the previousframe 422 provides an output to the amplifier 412. The output of theamplifier 412 is provided to the processor. The greater the drain of thephoto TFT 404, normally as a result of sensing light, results in agreater output of the amplifier 412. Referring to FIG. 14, an exemplarytiming for the writing and readout on the shared data line 400 isillustrated.

[0066] At low ambient lighting conditions and at dark lightingconditions, the integrated optical touch panel is not expected tooperate well to the touch of the finger because there will be aninsufficient (or none) difference between the signals from thesurrounding area and the touched area. To alleviate the inability toeffectively sense at the low and dark ambient lighting conditions alight pen or laser pointer may be used (e.g., light source), aspreviously described. The light source may be operably interconnected tothe display such as by a wire or wireless communication link. With thelight source operably interconnected to the display the intensity of thelight source may be controlled, at least in part, by feedback from thephoto-sensitive elements or otherwise the display, as illustrated inFIG. 15. When the display determines that sufficient ambient lightexists, such as ambient light exceeding a threshold value, the lightsource is turned “off”. In this manner, touching the light sourceagainst the display results in the same effect as touching a fingeragainst the display, namely, impeding ambient light from striking thedisplay. When the display determines that insufficient ambient lightexists, such as ambient light failing to exceed a threshold value, thelight source is turned “on”. In this manner, touching or otherwisedirecting the light from the light source against the display results ina localized increase in the received light relative to the ambient lightlevel. This permits the display to be operated in dark ambient lightingconditions or by feedback from the display. In addition, the intensityof the light from the light source may be varied, such as step-wise,linearly, non-linearly, or continuously, depending upon the ambientlighting conditions. Alternatively, the light source may include its ownambient light detector so that feedback from the display is unnecessaryand likewise communication between the light source and the display maybe unnecessary.

[0067] While using light from an external light source while beneficialit may still be difficult to accurately detect the location of theadditional light because of background noise within the system andvariable lighting conditions. The present inventors considered thissituation and determined that by providing light during differentframes, such as odd frames or even frames, or odd fields or even fields,or every third frame, or during selected frames, a more defineddifferential signal between the frames indicates the “touch” location.In essence, the light may be turned on and off in some manner, such asblinking at a rate synchronized with the display line scanning orframes. An exemplary timing for an odd/even frame arrangement is shownin FIG. 16. In addition, the illumination of some types of displaysinvolves scanning the display in a row-by-row manner. In such a case,the differential signal may be improved by modifying the timing of thelight pulses in accordance with the timing of the gate pulse (e.g.,scanning) for the respective pixel electrodes. For example, in atop-down scanning display the light pulse should be earlier when thelight source is directed toward the top of the display as opposed to thebottom of the display. The synchronization may be based upon feedbackfrom the display, if desired.

[0068] In one embodiment, the light source may blink at a ratesynchronized with the display line scanning. For example, the lightsource may use the same driver source as the image pixel electrodes. Inanother embodiment the use of sequential (or otherwise) frames may besubtracted from one another which results in significant differentbetween signal and ambient conditions. Preferably, the light sensitiveelements have a dynamic range greater than 2 decades, and morepreferably a dynamic range greater than 4 decades. If desired, thesystem may use two sequential fields of scanning (all lines) subtractedfrom the next two fields of scanning (all lines) so that all the linesof the display are used.

[0069] Another technique for effective operation of the display in darkor low level ambient conditions is using a pen or other device with alight reflecting surface that is proximate (touching or near touching)the display when interacting with the display. The light from thebacklight transmitted through the panel is then reflected back into thephoto-sensitive element and the readout signal will be greater at thetouch location than the surrounding area.

[0070] Referring to FIG. 17, another type of reflective liquid crystaldisplay, typically used on handheld computing devices, involvesincorporating a light guide in front of the liquid crystal material,which is normally a glass plate or clear plastic material. Normally, thelight guide is constructed from an opaque material having an index ofrefraction between 1.4 and 1.6, more typically between 1.45 and 1.50,and sometimes of materials having an index of refraction of 1.46. Thelight guide is frequently illuminated with a light source, frequentlydisposed to the side of the light guide. The light source may be anysuitable device, such as for example, a cold cathode fluorescent lamp,an incandescent lamp, and a light emitting diode. To improve the lightcollection a reflector may be included behind the lamp to reflect lightthat is emitted away from the light guide, and to re-direct the lightinto the light guide. The light propagating within the light guidebounces between the two surfaces by total internal reflections. Thetotal internal reflections will occur for angles that are above thecritical angle, measured relative to the normal to the surfaces, asillustrated in FIG. 18. To a first order approximation, the criticalangle β maybe defined by Sin(β)=1/n where n is the index of refractionof the light guide. Since the surfaces of the light guide are notperfectly smooth there will be some dispersion of the light, whichcauses some illumination of the display, as shown in FIG. 19.

[0071] The present inventors came to the realization that the criticalangle and the disruption of the total internal reflections may bemodified in such a manner as to provide a localized increase in thediffusion of light. Referring to FIG. 20, one suitable technique for thelocalized diffusion of light involves using a plastic pen to touch thefront of the display. The internally reflected light coincident with thelocation that the pen touches the display will significantly diffuse andbe directed toward the photo sensitive elements within the display. Theplastic pen, or other object including the finger or the eraser of apencil, preferably has an index of refraction within 0.5, morepreferably within 0.25, of the index of refraction of the light guide.For example, the index of refraction of the light guide may be between1.2 and 1.9, and more preferably between 1.4 and 1.6. With the twoindexes of refraction sufficiently close to one another the disruptionof the internal reflections, and hence amount of light directed towardthe photo-sensitive elements, is increased. In addition, the plastic penpreferably has sufficient reflectivity of light as opposed to beingnon-reflective material, such as for example, black felt.

[0072] Referring to FIG. 21, after further consideration the presentinventors were surprised to note that a white eraser a few millimetersaway from the light guide results in a darkened region with generallyconsistent optical properties while a white eraser in contact with thelight guide results in a darkened region with generally consistentoptical properties together with a smaller illuminated region. In thepreferred embodiment, the light sensitive elements are positioned towardthe front of the display in relation to the liquid crystal material (orotherwise the light valve or electroluminescent material) so that aclearer image may be obtained.⁵ It is to be understood that any suitablepointing device may be used. The illuminated region has an illuminationbrighter in relation to the remainder of the darkened region. Theilluminated region may be located by any suitable technique, such as forexample, a center of gravity technique.

[0073] After further consideration of the illuminated region the presentinventors came to the realization that when users use a “touch panel”display, there is a likelihood that the pointing device (or finger) may“hover” at a location above the display. Normally, during this hoveringthe user is not actually selecting any portion of the display, butrather still deciding where to select. In this manner, the illuminatedregion is beneficial because it provides a technique for thedetermination between when the user is simply “hovering” and the userhas actually touched (e.g., “touching”) the display.

[0074] Another potential technique for the determination between“hovering” and “touching” is to temporally model the “shadow” region(e.g., light impeded region of the display). In one embodiment, when theuser is typically touching the display then the end of the shadow willtypically remain stationary for a period of time, which may be used as abasis, at least in part, of “touching”. In another embodiment, theshadow will typically enlarge as the pointing device approaches thedisplay and shrinks as the pointing device recedes from the display,where the general time between enlarging and receding may be used as abasis, at least in part, of “touching”. In another embodiment, theshadow will typically enlarge as the pointing device approaches thedisplay and maintain the same general size when the pointing device istouching the display, where the general time where the shadow maintainsthe same size may be used as a basis, at least in part, of “touching”.In another embodiment, the shadow will typically darken as the pointingdevice approaches the display and maintain the same shade when thepointing device is touching the display, where the general time wherethe shadow maintains the same general shade may be used as a basis, atleast in part, of “touching”.

[0075] While attempting to consider implementation of such techniques ona handheld device it came to the inventor's surprise that the displayportion of a handheld device has a refresh rate generally less than therefresh rate of the portion of the handwriting recognition portion ofthe display. The handheld portion of the display may use any recognitiontechnique, such as Palm OS™ based devices. The refresh rate of thedisplay is typically generally 60 hertz while the refresh rate of thehandwriting portion of the display is typically generally 100 hertz.Accordingly, the light-sensitive elements should be sampled at asampling rate corresponding with the refresh rate of the respectiveportion of the display.

[0076] The technique described with respect to FIG. 20 operatesreasonably well in dark ambient lighting conditions, low ambientlighting conditions, regular ambient lighting conditions, and highambient lighting conditions. During regular and high ambient lightingconditions, the display is alleviated of a dependency on the ambientlighting conditions. In addition, with such lighting the illuminationpoint is more pronounced and thus easier to extract. Unfortunately,during the daytime the ambient light may be sufficiently high causingthe detection of the pointing device difficult. In addition, shades ofthe ambient light may also interfere with the detection techniques.

[0077] The present inventors considered improving the robustness of thedetection techniques but came to the realization that with sufficient“noise” in the system the creation of such sufficiently robusttechniques would be difficult. As opposed to the traditional approach ofimproving the detection techniques, the present inventors came to therealization that by providing light to the light guide of a limitedselection of wavelengths and selectively filtering the wavelengths oflight within the display the difference between touched and un-touchedmay be increased. As an initial matter the light from the light sourceprovided to the light guide is modified, or otherwise filtered, toprovide a single color. Alternatively, the light source may providelight of a range of wavelengths, such as 600-700 nm, or 400-500 and530-580, or 630. Typically, the light provided to the light guide has arange of wavelengths (in any significant amount) less than white lightor otherwise the range of wavelengths of ambient light. Accordingly,with the light provided to the light guide having a limited color gamut(or reduced color spectrum) the touching of the pointing device on thedisplay results in the limited color gamut light being locally directedtoward the light-sensitive elements. With a limited color gamut lightbeing directed toward the display as a result of touching the lightguide (or otherwise touching the front of the display), a color filtermay be included between the light guide and the light-sensitive elementsto filter out at least a portion of the light not included within thelimited color gamut. In other words, the color filter reduces thetransmission of ambient light to an extent greater than the transmissionof light from the light source or otherwise within the light guide. Forexample, the ambient light may be considered as “white” light while thelight guide has primarily “red” light therein. A typical transmission ofa red color filter for ambient white light may be around 20%, while thesame color filter will transmit about 85% of the red light. Preferablythe transmission of ambient light through the color filter is less than75% (greater than 25% attenuation) (or 60%, 50%, 40%, 30%) while thetransmission of the respective light within the light guide is greaterthan 25% (less than 25% attenuation) (or 40%, 50%, 60%, 70%), so that inthis manner there is sufficient attenuation of selected wavelengths ofthe ambient light with respect to the wavelengths of light within thelight guide to increase the ability to accurately detect the touching.

[0078] In another embodiment, the light source to the light guide mayinclude a switch or otherwise automatic modification to “white” lightwhen operated in low ambient lighting conditions. In this manner, thedisplay may be more effective viewed at low ambient lighting conditions.

[0079] In another embodiment, the present inventors determined that ifthe light source providing light to the display was modulated in somefashion an improvement in signal detection may be achieved. For example,a pointing device with a light source associated therewith may modulatethe light source in accordance with the frame rate of the display. Witha frame rate of 60 hertz the pointing device may for example modulatethe light source at a rate of 30 hertz, 20 hertz, 10 hertz, etc. whichresults in additional light periodically being sensed by the lightsensitive elements. Preferably, the light source is modulated(“blinked”) at a rate synchronized with the display line scanning, anduses the same raw drivers as the image thin-film transistors. Theresulting data may be processed in a variety of different ways.

[0080] In one embodiment, the signals from the light sensitive elementsare used, as captured. The resulting improvement in signal to backgroundratio is related to the pulse length of the light relative to the frametime. This provides some additional improvement in signal detectionbetween the light generated by the pointing device relative to theambient light (which is constant in time).

[0081] In another embodiment, multiple frames are compared against oneanother to detect the presence and absence of the additional lightresulting from the modulation. In the case of subsequent frames(sequential or non-sequential), one without additional light and onewith additional light, the data from the light sensitive elements may besubtracted from one another. The improvement in signal to backgroundratio is related to the periodic absence of the additional light. Inaddition, this processing technique is especially suitable for lowambient lighting and high ambient lighting conditions. Preferably thedynamic range of the sensors is at least 4 decades, and two sequentialframes with additional light and two sequential frames withoutadditional light are used so that all of the scanning lines areencompassed. When the system charges a sensor it takes a whole frame forit to discharge by the light. Since the first line will start at timezero and take a frame time, the last line will be charged after almost aframe and will take another frame time to discharge. Therefore, thesystem should preferably use two frames with additional illumination andthen two frames without additional illumination.⁶

[0082] All references cited herein are hereby incorporated by reference.

[0083] The terms and expressions which have been employed in theforegoing specification are used therein as terms of description and notof limitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

1. A liquid crystal device comprising: (a) a front electrode layer; (b)a rear electrode layer; (c) a liquid crystal material located betweensaid front electrode layer and said rear electrode layer; (d) changingan electrical potential between said rear electrode layer and said frontelectrode layer to selectively modify portions of said liquid crystalmaterial to change the polarization of the light incident thereon; and(e) a plurality of light sensitive elements located together with saidrear electrode layer.
 2. The device of claim 1 wherein each of saidlight sensitive elements include a transistor.
 3. The device of claim 2wherein each of said light sensitive elements includes a firsttransistor that senses ambient light, and a second transistor that isinhibited from sensing ambient light with respect to said firsttransistor.
 4. The device of claim 3 wherein at least one of said firsttransistor and said second transistor is a thin-film transistor.
 5. Thedevice of claim 4 wherein said thin-film transistor is amorphoussilicon.
 6. The device of claim 3 wherein a terminal of said firsttransistor is connected to a terminal of said second transistor with afirst conductor.
 7. The device of claim 6 wherein said first conductoris capacitively coupled to a common line.
 8. The device of claim 7wherein said common line has a voltage potential less than said firstconductor.
 9. The device of claim 1 wherein said device is an activematrix liquid crystal device.
 10. A light sensitive display comprising:(a) a light valve including a front polarizing element, a rearpolarizing element, and light rotating material located between saidfirst polarizing element and said rear polarizing element; and (b) aplurality of light sensitive elements located between said rearpolarizing element and said light rotating material.
 11. The display ofclaim 10 wherein said display is an active matrix liquid crystal device.12. The display of claim 10 wherein each of said light sensitiveelements includes a first transistor that senses ambient light, and asecond transistor that is inhibited from sensing ambient light withrespect to said first transistor.
 13. The display of claim 10 furthercomprising a processor that receives information from said lightsensitive elements and determines at least one of regions of saiddisplay where ambient light is inhibited from reaching said lightsensitive elements and regions of said display where light in excess ofsaid ambient light reaches said light sensitive elements.
 14. Thedisplay of claim 10 further comprising a processor that receivesinformation from said light sensitive elements and determines regions ofsaid display where ambient light is inhibited from reaching said lightsensitive elements.
 15. The display of claim 10 further comprising aprocessor that receives information from said light sensitive elementsand determines regions of said display where light in excess of saidambient light reaches said light sensitive elements.
 16. A lightsensitive display comprising: (a) a light valve including a frontelectrode layer, a rear electrode layer, and light rotating materiallocated between said first electrode layer and said rear electrodelayer; (b) said front and rear electrode layer defining a plurality ofpixels within said light rotating material; and (c) a plurality of lightsensitive elements located within said light sensitive display locatedat least partially between said pixels.
 17. The display of claim 16wherein said display is a reflective liquid crystal device.
 18. Thedisplay of claim 16 wherein said plurality of light sensitive elementslocated said at least partially between said pixels, with respect to aperpendicular direction to the front of said display.
 19. The display ofclaim 16 wherein each of said light sensitive elements includes a firsttransistor that senses ambient light, and a second transistor that isinhibited from sensing ambient light with respect to said firsttransistor.
 20. The display of claim 16 further comprising a processorthat receives information from said light sensitive elements anddetermines at least one of regions of said display where ambient lightis inhibited from reaching said light sensitive elements and regions ofsaid display where light in excess of said ambient light reaches saidlight sensitive elements.
 21. The display of claim 16 further comprisinga processor that receives information from said light sensitive elementsand determines regions of said display where ambient light is inhibitedfrom reaching said light sensitive elements.
 22. The display of claim 16further comprising a processor that receives information from said lightsensitive elements and determines regions of said display where light inexcess of said ambient light reaches said light sensitive elements. 23.A light sensitive display comprising: (a) a light valve including afront polarizing element, a rear polarizing element, and light rotatingmaterial located between said first polarizing element and said rearpolarizing element; and (b) a plurality of light sensitive elementslocated between said front polarizing element and said light rotatingmaterial.
 24. The display of claim 23 wherein each of said lightsensitive elements includes a first transistor that senses ambientlight, and a second transistor that is inhibited from sensing ambientlight with respect to said first transistor.
 25. The display of claim 23further comprising a processor that receives information from said lightsensitive elements and determines at least one of regions of saiddisplay where ambient light is inhibited from reaching said lightsensitive elements and regions of said display where light in excess ofsaid ambient light reaches said light sensitive elements.
 26. A liquidcrystal device comprising: (a) a front electrode layer; (b) a rearelectrode layer comprising a plurality of pixel electrodes; (c) a liquidcrystal material located between said front electrode layer and saidrear electrode layer; (d) a front polarizing element located toward thefront of said liquid crystal device relative to said front electrodelayer; (e) a rear polarizing element located toward the rear of saidliquid crystal device relative to said rear electrode layer; (f)changing an electrical potential between said rear electrode layer andsaid front electrode layer to selectively modify portions of said liquidcrystal material to change the polarization of the light incidentthereon; and (g) a plurality of light sensitive elements located atleast partially between said pixel electrodes, with respect to aperpendicular direction to the front of said device, and between saidliquid crystal material and said rear polarizing element.
 27. A lightsensitive display comprising: (a) said display selectively causingpixels to provide light; (b) a plurality of light sensitive elementslocated within said display, wherein said light sensitive elements aretransistors.
 28. The display of claim 27 wherein said display is aliquid crystal display.
 29. The display of claim 27 wherein said lightvalve includes liquid crystal material.
 30. The display of claim 27wherein each of said light sensitive elements includes a firsttransistor that senses ambient light, and a second transistor that isinhibited from sensing ambient light with respect to said firsttransistor.
 31. A light sensitive display comprising: (a) said displayselectively causing pixels to provide light; (b) a plurality of lightsensitive elements located within said display; (c) a processor thatreceives information from said light sensitive elements and determinesregions of said display where ambient light is inhibited from reachingsaid light sensitive elements and regions of said display where light inexcess of said ambient light reaches said light sensitive elements. 32.The display of claim 31 wherein said display is a liquid crystaldisplay.
 33. The display of claim 32 wherein said liquid crystal displayis active matrix.
 34. The display of claim 32 wherein said liquidcrystal display is passive.
 35. A light sensitive display comprising:(a) said display selectively causing pixels to provide light; (b) aplurality of light sensitive elements located within said display; (c) aprocessor that receives information from said light sensitive elementsand determines regions of said display where light in excess of saidambient light reaches said light sensitive elements.
 36. The lightsensitive display of claim 35 said light in excess results from anoptical pointing device.
 37. The light sensitive display of claim 36wherein said optical pointing device is a laser pointer.
 38. A liquidcrystal device comprising: (a) a front electrode layer; (b) a rearelectrode layer comprising a plurality of pixel electrodes; (c) a liquidcrystal material located between said front electrode layer and saidrear electrode layer; and (d) a plurality of light sensitive elementslocated within said display wherein each of said light sensitiveelements includes a first transistor that senses ambient light, a secondtransistor that is inhibited from sensing ambient light with respect tosaid first transistor.
 39. The device of claim 38 wherein a terminal ofsaid first transistor is connected to a terminal of said secondtransistor with a first conductor.
 40. The device of claim 39 whereinsaid first conductor is capacitively coupled to another line with acapacitor.
 41. The device of claim 40 wherein said another line has avoltage potential less than said first conductor.
 42. The device ofclaim 38 wherein said device is an active matrix liquid crystal device.43. A display comprising: (a) said display selectively causing pixels toprovide light; and (b) a plurality of light sensitive elements locatedwithin said display wherein each of said light sensitive elementsincludes a first transistor that senses ambient light, and a secondtransistor that is inhibited from sensing ambient light with respect tosaid first transistor.
 44. The device of claim 43 wherein said device isat least one of multi-domain vertical alignment liquid crystal display,patterned vertical alignment liquid crystal display, in-plane switchingliquid crystal display, super-twisted nematic type liquid crystaldisplay, plasma display, electroluminescent display, liquid crystal onsilicon display, and reflective liquid crystal device.
 45. A lightsensitive display comprising: (a) said display selectively causingpixels to provide light; (b) a backlight within said display; (c) atleast one light sensitive element located within said display; and (d)modifying the intensity of said backlight based upon said lightsensitive element.
 46. A light sensitive display comprising: (a) saiddisplay selectively causing pixels to provide light; (b) a plurality oflight sensitive elements located within said display; (c) a processorthat receives information from said light sensitive elements anddetermines at least one of: (i) regions of said display where ambientlight is inhibited from reaching said light sensitive elements, and (ii)regions of said display where light in excess of said ambient lightreaches said light sensitive elements; (d) a plurality of pixelelectrodes within said display wherein data provided to said pixelelectrodes is modified in a manner in a manner consistent with the sizeof said pixel electrodes within said display.
 47. The display of claim46 wherein the data corresponding with said pixel electrodes having asize decreased by said light sensitive elements is modified.
 48. Thedisplay of claim 47 wherein said data corresponding with said pixelelectrodes having a decreased size is increased.
 49. The display ofclaim 47 wherein said data corresponding with said pixel electrodeshaving a decreased size remains unchanged while the data correspondingwith a plurality of other pixel electrodes is modified.
 50. The displayof claim 49 wherein said data corresponding with said other pixelelectrodes is decreased.
 51. A liquid crystal device comprising: (a) afront electrode layer; (b) a rear electrode layer comprising a pluralityof pixel electrodes; (c) a liquid crystal material located between saidfront electrode layer and said rear electrode layer; (d) a plurality oflight sensitive elements located within said display wherein each ofsaid light sensitive elements corresponds with a selected one of saidpixel electrodes; and (e) a plurality of elongate conductors each ofwhich is electrically interconnected with a respective one of said lightsensitive elements wherein said elongate conductors are arranged in amanner consistent with the pattern of said pixel electrodes.
 52. Thedevice of claim 51 wherein said elongate conductors are said arranged atleast within every 12^(th) pixel of said display.
 53. The device ofclaim 52 wherein said elongate conductors are said arranged at leastwithin every 9^(th) pixel of said display.
 54. The device of claim 53wherein said elongate conductors are said arranged at least within every6^(th) pixel of said display.
 55. The device of claim 54 wherein saidelongate conductors are said arranged at least within every 3^(rd) pixelof said display.
 56. The device of claim 52 wherein there are at leastfour elongate conductors.
 57. The device of claim 53 wherein there areat least four elongate conductors.
 58. The device of claim 54 whereinthere are at least four elongate conductors.
 59. The device of claim 55wherein there are at least four elongate conductors.
 60. The device ofclaim 51 wherein said elongate conductors are said arranged over amajority of said device.
 61. The device of claim 51 wherein at least oneof said plurality of elongate conductors is free from beingoperationally interconnected with any of said light sensitive elements.62. The device of claim 51 wherein at least one of said plurality ofelongate conductors is free from being operationally interconnected withreadout electronics.
 63. The device of claim 51 wherein the spacingbetween at least one pair of pixel electrodes having at least one saidelongate conductors there between is substantially the same as thespacing between another pair of pixel electrodes free from having one ofsaid elongate conductors there between.
 64. A liquid crystal devicecomprising: (a) a front electrode layer; (b) a rear electrode layercomprising a plurality of pixel electrodes; (c) a liquid crystalmaterial located between said front electrode layer and said rearelectrode layer; (d) a plurality of light sensitive elements locatedwithin said display wherein each of said light sensitive elementscorresponds with a selected one of said pixel electrodes; (e) aplurality of elongate conductors each of which is electricallyinterconnected with a respective one of said light sensitive elements;and (f) said plurality of elongate conductors each of which is alsoelectrically interconnected with at least a respective one of said pixelelectrodes.
 65. The device of claim 64 wherein said elongate conductorsare arranged at least within every 12^(th) pixel of said display. 66.The device of claim 65 wherein said elongate conductors are arranged atleast within every 9^(th) pixel of said display.
 67. The device of claim66 wherein said elongate conductors are arranged at least within every6^(th) pixel of said display.
 68. The device of claim 67 wherein saidelongate conductors are arranged at least within every 3^(rd) pixel ofsaid display.
 69. The device of claim 64 wherein data is simultaneouslyprovided to a respective pair of light sensitive elements and pixelelectrodes.
 70. The device of claim 64 wherein data is provided to arespective pair of light sensitive elements and pixel electrodes duringa scan time of a scanning electrode.
 71. A liquid crystal devicecomprising: (a) a front electrode layer; (b) a rear electrode layercomprising a plurality of pixel electrodes; (c) a liquid crystalmaterial located between said front electrode layer and said rearelectrode layer; (d) a plurality of light sensitive elements locatedwithin said display wherein each of said light sensitive elementscorresponds with a selected one of said pixel electrodes; and (e)wherein data is provided to a respective pair of light sensitiveelements and pixel electrodes during a scan time of a scanningelectrode.
 72. The device of claim 71 further comprising a plurality ofelongate conductors each of which is electrically interconnected with arespective one of said light sensitive elements.
 73. The device of claim72 further comprising said plurality of elongate conductors each ofwhich is also electrically interconnected with at least a respective oneof said pixel electrodes.
 74. A light sensitive display comprising: (a)said display selectively causing pixels to provide light during a frame;(b) a plurality of light sensitive elements located within said display;(c) a processor that receives information from said light sensitiveelements for said frame and determines at least one of: (i) regions ofsaid display where ambient light is inhibited from reaching said lightsensitive elements; (ii) regions of said display where light in excessof said ambient light reaches said light sensitive elements; (d) whereinsaid determination is further based upon data from a previous frame. 75.The display of claim 74 wherein said previous frame is the immediatelyproceeding frame.
 76. A light sensitive display comprising: (a) saiddisplay selectively causing pixels to provide light during a currentframe; (b) a plurality of light sensitive elements located within saiddisplay; (c) a processor that receives information from said lightsensitive elements for said current frame and determines a locationwhere said display has been touched; (d) wherein said determination isfurther based upon data from a previous frame.
 77. The display of claim76 wherein said previous frame is the immediately proceeding frame. 78.The display of claim 76 wherein said determination is made based upon achange in the data provided to one of said light sensitive elementsduring said previous frame and the data readout from said one of saidlight sensitive elements during said current frame.
 79. A lightsensitive display comprising: (a) said display selectively causingpixels to provide; (b) a plurality of light sensitive elements locatedwithin said display; (c) a processor that receives information from saidlight sensitive elements and determines a location where said displayhas been touched; (d) wherein said determination is further based upondata provided to said light sensitive elements prior to said receivingsaid information from said light sensitive elements.
 80. The display ofclaim 79 wherein said display is selectively illuminated during a timebetween said receiving said information and providing said data.
 81. Thedisplay of claim 79 wherein said determination is made based upon achange in the data provided to one of said light sensitive elementsduring a previous frame and the data readout from said one of said lightsensitive elements during a current frame.
 82. A light sensitive displaycomprising: (a) said display selectively causing pixels to providelight; (b) at least one light sensitive element located within saiddisplay; and (d) modifying the intensity of a portable external lightsource directed at said display based upon said at least one lightsensitive element.
 83. The display of claim 82 wherein said display issized to fit in the palm of the hand.
 84. The display of claim 82wherein said portable external light source is electrically connected tosaid display.
 85. The display of claim 84 wherein said light source is agenerally elongate device.
 86. The display of claim 82 wherein saidportable external light source is operably interconnected to saiddisplay via a wireless communication link.
 87. The display of claim 82wherein said portable external light source selectively provides lightbased upon ambient light conditions.
 88. The display of claim 87 whereinsaid portable external light source provides light if the ambient lightconditions below a threshold.
 89. A light sensitive display comprising:(a) said display selectively causing pixels to provide light; (b) atleast one light sensitive element located within said display; and (d)modifying the intensity of a portable external light source directed atsaid display based upon ambient lighting conditions.
 90. The display ofclaim 89 wherein said display is sized to fit in the palm of the hand.91. The display of claim 89 wherein said portable external light sourceis electrically connected to said display.
 92. The display of claim 89wherein said portable external light source is operably interconnectedto said display via a wireless communication link.
 93. A light sensitivedisplay comprising: (a) said display selectively causing pixels toprovide light; (b) at least one light sensitive element located withinsaid display; and (d) modifying the intensity of an external lightsource directed at said display based upon the addressing of saiddisplay.
 94. The display of claim 93 wherein said display is sized tofit in the palm of the hand.
 95. The display of claim 93 wherein saidexternal light source is electrically connected to said display.
 96. Thedisplay of claim 93 wherein said external light source is operablyinterconnected to said display via a wireless communication link. 97.The display of claim 93 wherein said addressing includes the scanning ofsaid display.
 98. The display of claim 93 wherein said addressingincludes different frames.
 99. The display of claim 93 wherein saidaddressing includes odd and even frames or fields.
 100. The display ofclaim 93 wherein said addressing includes where in said display saidlight source is directed.
 101. The display of claim 100 wherein saidwhere in said display is the top and bottom of said display.
 102. Thedisplay of claim 100 wherein said addressing is further based upon dataprovided to said light source from said display.
 103. A liquid crystaldevice comprising: (a) a front electrode layer; (b) a rear electrodelayer comprising a plurality of pixel electrodes; (c) a liquid crystalmaterial located between said front electrode layer and said rearelectrode layer; (d) changing an electrical potential between said rearelectrode layer and said front electrode layer to selectively modifyportions of said liquid crystal material to change the polarization ofthe light incident thereon; (e) a light guide together with anassociated light source located in front of said front electrode layerto provide light thereto; (f) a plurality of light sensitive elementslocated within said display; and (g) wherein the total internalreflections of said light guide is disrupted by contacting said displaywith a pointing device, where the pointing device has an index ofrefraction within 0.5 of the index of refraction of said light guide.104. The device of claim 103 wherein the index of refraction of saidlight guide is between 1.4 and 1.6
 105. The device of claim 104 whereinthe index of refraction of said light guide is between 1.45 and 1.50.106. The device of claim 104 wherein the index of refraction of saidpointing device is between 1.2 and 1.9.
 107. The device of claim 106wherein the index of refraction of said pointing device is between 1.4and 1.6.
 108. A liquid crystal device comprising: (a) a front electrodelayer; (b) a rear electrode layer comprising a plurality of pixelelectrodes; (c) a liquid crystal material located between said frontelectrode layer and said rear electrode layer; (d) changing anelectrical potential between said rear electrode layer and said frontelectrode layer to selectively modify portions of said liquid crystalmaterial to change the polarization of the light incident thereon; (e) alight guide together with an associated light source located in front ofsaid front electrode layer to provide light thereto; (f) a plurality oflight sensitive elements located within said display; and (g) aprocessor determining the location of touching of said display bysensing a light inhibited region by said light sensitive elementswherein light has been inhibited from reaching said light sensitiveelements with an interior region to said inhibited region having greaterillumination.
 109. A liquid crystal device comprising: (a) a frontelectrode layer; (b) a rear electrode layer comprising a plurality ofpixel electrodes; (c) a liquid crystal material located between saidfront electrode layer and said rear electrode layer; (d) changing anelectrical potential between said rear electrode layer and said frontelectrode layer to selectively modify portions of said liquid crystalmaterial to change the polarization of the light incident thereon; (e) aplurality of light sensitive elements located within said display; and(f) a processor determining the location of touching of said display bysensing a light inhibited region by said light sensitive elementswherein light has been inhibited from reaching said light sensitiveelements with an interior region to said inhibited region having greaterillumination.
 110. A light sensitive display comprising: (a) saiddisplay selectively causing pixels to provide light; (b) a plurality oflight sensitive elements located within said display; (c) a processorthat receives information from said light sensitive elements anddetermines regions of said display where ambient light is inhibited fromreaching said light sensitive elements, wherein data from said lightsensitive elements is temporally analyzed.
 111. The display of claim 110wherein said temporal analysis determines whether a pointing device is“hovering” with respect to said display or touching said display. 112.The display of claim 110 wherein said temporal analysis determineswhether a pointing device remains stationary for a period of time. 113.The display of claim 110 wherein said temporal analysis determineswhether a pointing device approaches the display and thereafter recedesfrom the display.
 114. The display of claim 113 wherein the general timebetween approaching and receding is used as a basis for said pointingdevice touching said display.
 115. The display of claim 110 wherein saidtemporal analysis determines whether a pointing device approaches saiddisplay and said pointing device maintains the same general size, wherethe general time when the shadow maintains the same size is used as abasis for said pointing device touching said display.
 116. The displayof claim 110 wherein said display is a liquid crystal display.
 117. Thedisplay of claim 110 wherein said liquid crystal display is activematrix.
 118. The display of claim 110 wherein said liquid crystaldisplay is passive.
 119. A light sensitive display comprising: (a) saiddisplay selectively causing pixels to provide light; (b) a plurality oflight sensitive elements located within said display; (c) a samplingcircuit that reads data from said plurality of light sensitive elementsat a rate corresponding with the refresh rate of the correspondingportion of said display, wherein the display includes at least twodifferent refresh rates.
 120. A liquid crystal device comprising: (a) afront electrode layer; (b) a rear electrode layer comprising a pluralityof pixel electrodes; (c) a liquid crystal material located between saidfront electrode layer and said rear electrode layer; (d) changing anelectrical potential between said rear electrode layer and said frontelectrode layer to selectively modify portions of said liquid crystalmaterial to change the polarization of the light incident thereon; (e) aplurality of light sensitive elements located within said display; (f) alight guide together with an associated light source located in front ofsaid front electrode layer to provide light thereto, wherein said lighthas a color spectrum less than ambient light; and (g) a color filterpositioned between said light guide and at least one of said lightsensitive elements, wherein said color reduces the transmission of saidambient light to an extent greater than said light from said lightsource.⁷
 121. The device of claim 120 wherein said ambient light iswhite light.
 122. The device of claim 120 wherein said color filter hasa transmission of said ambient light less than 75%.
 123. The device ofclaim 120 wherein said color filter has a transmission of said ambientlight less than 60%.
 124. The device of claim 120 wherein said colorfilter has a transmission of said ambient light less than 50%.
 125. Thedevice of claim 120 wherein said color filter has a transmission of saidambient light less than 40%.
 126. The device of claim 120 wherein saidcolor filter has a transmission of said ambient light less than 30%.127. The device of claim 120 wherein said color filter has atransmission of said light from said light source greater than 25%. 128.The device of claim 120 wherein said color filter has a transmission ofsaid light from said light source greater than 40%.
 128. The device ofclaim 120 wherein said color filter has a transmission of said lightfrom said light source greater than 50%.
 130. The device of claim 120wherein said color filter has a transmission of said light from saidlight source greater than 60%.
 131. The device of claim 120 wherein saidcolor filter has a transmission of said light from said light sourcegreater than 70%.
 132. A light sensitive display system comprising: (a)said display selectively causing pixels to provide light duringsubsequent frames; (b) a plurality of light sensitive elements locatedwithin said display; (c) a first amount of additional light provided tosaid light sensitive elements during at least one of said subsequentframes; (d) a second amount of said additional light selectivelyprovided to said light sensitive elements during at least one other ofsaid subsequent frames, wherein said first and second additional lightare different; and (e) said display system determining the location ofsaid additional light on said display based upon sensing a portion ofsaid first and second additional light.⁸
 133. The display of claim 132wherein said first amount of said additional light is greater than saidsecond amount of said additional light.
 134. The display of claim 132wherein said subsequent frames are sequential frames.
 135. A method ofsensing with a display comprising: (a) a plurality of light sensitiveelements located within said display; (b) modifying an amount ofadditional light provided to said light sensitive elements duringmultiple frames; and (c) system determining the location of saidadditional light on said display based upon sensing said additionallight.⁹
 136. The display of claim 135 wherein said first amount of saidadditional light is greater than said second amount of said additionallight.
 137. The display of claim 135 wherein said multiple frames arenon-sequential.
 138. The display of claim 135 wherein said multipleframes are sequential.
 139. The display of claim 135 wherein saidmodifying includes providing no-light.
 140. A liquid crystal devicecomprising: (a) a front electrode layer; (b) a rear electrode layercomprising a plurality of pixel electrodes, wherein a first plurality ofsaid pixel electrodes is associated with blue, a second plurality ofsaid pixel electrodes is associated green, and a third plurality of saidpixel electrodes is associated with red; (c) a liquid crystal materiallocated between said front electrode layer and said rear electrodelayer; (d) a plurality of light sensitive elements located within saiddisplay wherein each of said light sensitive elements corresponds with aselected one of said pixel electrodes, wherein at least one of: (i) agreater number of said light sensitive elements are associated with saidblue pixel electrodes, than said green pixel electrodes; (ii) a greaternumber of said light sensitive elements are associated with said bluepixel electrodes, than said red pixel electrodes; (iii) a greater numberof said light sensitive elements are associated with said blue pixelelectrodes, than non-blue said pixel electrodes.¹⁰